Increasingly, test devices in the form of reagent strips are being used to provide convenient and rapid analysis of various types of samples, including samples of biological, industrial and automotive fluids, wines and the like. Diagnostic test devices designed for detecting various clinically significant substances or constituents in biological fluids, such as urine and blood, including lysed and unlysed blood, blood plasma and blood serum have in many cases supplanted prior wet chemistry techniques which were both cumbersome and time-consuming. The diagnostic test devices or reagent strips have thus assisted in the fast, inexpensive and accurate diagnosis and treatment of disease.
Conventional test devices generally comprise an absorbent or porous matrix incorporated with indicator reactions, usually of a colorimetric nature. The sample to be tested is contacted with the matrix, such as by momentary emersion, where the sample is liquid, and an indicator response is observed after a period of time. For example, in the detection of occult blood in urine a diagnostic test device can be employed which comprises an absorbent paper impregnated with o-toluidine and peroxide. When this test device is wetted with urine containing occult blood, decomposition of the peroxide occurs with the accompanying oxidation of the o-toluidine to provide a color response. This test is sensitive and extremely useful in diagnosing urinary tract disorders.
For ease in handling, the absorbent or porous matrix, sometimes called a "carrier matrix", is advantageously affixed to an insoluble support member such as an organoplastic strip, e.g., polystyrene, by suitable means such as double-faced adhesive tape. Optically transparent substrate material known as Trycite, polystyrene film made by Dow Chemical Company, is preferred. The support member normally has a thickness of about 0.19 mm, a width of about 5 mm and a length which can vary depending on the intended use, the number of reagent areas present, etc.
Currently, test devices are being made by the Ames Division of Miles Laboratories, Inc. which have lengths of about 85.5 mm and about 82.5 mm. Obviously, based on these dimensions and the materials involved, such test devices tend to be small, elongated and flexible in nature. While these test devices are easily manageable during manual handling operations, automated handling has presented a significant problem.
With the need for automated equipment employing test devices for determining constituents in fluids, especially for performing multiple diagnostic tests, it is essential that a mechanical system be devised which is capable of rapidly, accurately and reliably handling one test device at a time. The removal of a single test device from a cartridge, container or magazine containing multiple test devices to permit the transfer of a single test device to another portion of the system for contact with sample to be tested, is, therefore, a key to automating such testing.
In one very special case, i.e., very small test devices which contain a single reagent area, apparatus has been developed for ejecting one test device at a time from a magazine or cartridge containing multiple test devices of a similar nature. Generally, the substrate for such test devices is only slightly larger than the dimensions of the absorbent matrix, which normally measures about 5 mm by about 10 mm. Typically, such ejection devices contain means for ejecting or pushing a test device from a magazine or container in which multiple test devices are spring loaded or gravity fed such that one test device at a time can be ejected when pressure is applied to the edge of either the bottommost or topmost test device.
For standard test devices having elongated dimensions, as set forth above, however, there is no apparatus available which is totally effective for removing one test device at a time from a cartridge or magazine containing other test devices. Ejection systems employed in the special case of very small test devices are not effective for use with test devices of normal dimensions.
In U.S. Ser. No. 263,033, filed May 13, 1981, now abandoned, test device handling apparatus and a process were disclosed involving a cartridge or magazine holder capable of retaining multiple test devices in stacked position inside the holder by detents located on opposite sides of an opening in the bottom of the holder. By applying vacuum pick up means the bottommost test device in the cartridge or magazine could be bent or flexed sufficiently to cause the bottommost test device to pass over the detents and be removed from the cartridge or magazine while retaining the other test devices in the cartridge or magazine. While the disclosed apparatus and method permitted a single test device to be removed from a holder containing multiple test devices the position and operation of the vacuum pick up means were somewhat critical in order to avoid disruption of the test devices remaining inside the container or cartridge when the bottommost test device was removed from the cartridge. The design of this prior art apparatus resulted in a minimum of vibration. Nevertheless, the system, like other prior art systems, was sensitive to alignment of the reagent test devices. Repeated removal of test devices and the accompanying vibration would sometimes result in test device alignment problems for the vacuum pick up means. Moreover, only a relative small number of test devices could be stored in the cartridges employed in connection with the aforementioned test device handling system. The reason for this is that the configuration of the test devices, which contain one or more reagent matrix areas at one end having a thickness greater than at the other end, caused the test devices to become skewed in the cartridges or containers if an attempt was made to stack a large number of test devices. Accordingly, to avoid alignment problems of the reagent test devices in the containers or cartridges the number of test devices had to be limited to a relatively small number of reagent test devices.
Accordingly, for applications requiring automation there has been a need for foolproof test device handling apparatus capable of removing a single flexible member from a cartridge or magazine such that flexible member can then be transferred to another portion of the system.